When exporting a rig from Blender to UE4 and using UE4's IK system, my limbs break
I've found that a Blender script here enabled me to export a Make Human originated mesh with a skeleton that was entirely compatible with the UE4 skeleton having the correct bone names and bone rolls. It requires Blender 2.8 though and I tested it with UE 4.21.2 and the free animations that came with UE including the Animation Starter Pack.